In a biometric authentication, a position of input biometric information may be different from that of enrollment biometric information because of inputting condition or environment of a user. The difference of the positions may cause an authentication error. In a palm vein authentication, a guide for guiding a hand posture may be used in order to reduce influence of the position difference. However, with respect to a user of which hand is larger than the guide, an image of a hand without a part thereof may be captured. In this case, a possibility of the authentication error may be increased. It is difficult to provide a guide to a mobile electronic device. And so, there is disclosed a technology of a palm authentication for reducing influence of the position difference (for example, see Japanese Patent Application Publication No. 2010-26658 and Japanese Patent Application Publication No. 2015-28724).